Numerous mixer devices of the above-mentioned type including a thermostatic element have already been proposed.
Such mixer devices are described and shown in patent documents FR-A No. 2 174 134 and FR-A No. 2 295 327, for example.
Accompanying FIG. 1 is a diagram of a conventional mixer device including a thermostatic element, in accordance with the description of patent document FR-A No. 2 174 134.
The mixer device shown in FIG. 1 comprises: a body 10; a thermal expansion element 30; and a slide 50 fixed to said element.
The body 10 defines an internal chamber 12 which is generally circularly cylindrical about an axis 11. The chamber 12 is closed axially at one end by the bottom 13 of the body and at its other end by a cap 14 which is screwed onto the body at 15.
The body 10 has a first radial inlet orifice 16 and a second radial inlet orifice 17 which connect the internal chamber 12 respectively to a hot water inlet connection 18 and to a cold water inlet connection 19.
The radial orifices 16 and 17 are spaced apart axially.
The body 10 also has an outlet orifice 20 which connects the internal chamber 12 to an outlet connection 21 via which the fluid mixture is evacuated.
The thermal expansion element 30 is received in the chamber 12 coaxially about the axis 11. It is resiliently biassed by a spring 31 to press against a temperature adjustment member 70 carried by the cap 14. The spring 31 is inserted between the bottom 13 of the body and an outwardly projecting collar 32 on the element 30.
The slide 50 comprises a plate 52 and a sleeve 51 which is coaxial about the axis 11. The plate is located inside the sleeve 51 to which it is fixed, and extends transversely to the axis 11. The plate 52 is perforated at 53 to allow fluid to pass therethrough. The plate 52 is in addition screwed, at 54, onto the element 30 in order to follow the axial displacements thereof due to thermal expansion.
The outer surface of the sleeve 51 rests against a bush 60 which is coaxial with the axis 11. The outer surface of the bush 60 rests in turn via a sealing ring 61 against the inside surface of the chamber 12, between the radial inlet orifices 16 and 17 in order to separate them.
The temperature adjustment member 70 serves to adjust the axial position of the temperature expansion element 30 and of the slide 50, thereby disengaging the radial inlet orifices 16 and 17 in proportion to the flow rates of hot fluid and cold fluid that are required to obtain the desired outlet temperature.
If there are fluctuations in the flow rates or the temperatures of the hot and cold fluids, the thermal expansion element 30 changes the ratio between the free cross-sections of the inlet orifices 16 and 17 so as to modify the proportions of the mixture in order to maintain the desired temperature in the outlet mixture.
Patent document U.S. Pat. No. 2,657,859 describes a generally similar mixer device. The device described in document U.S. Pat. No. 2,657,859 additionally includes two annular elements which are urged to press against the slide via pressure washers. The annular elements are thus urged in a direction suitable for opening the hot and cold fluid passages.
Mixer devices of the type illustrated in accompanying FIG. 1 as described above have given good service.
However, the Applicant has observed that such prior mixer devices suffer from a serious drawback due to the fact that they do not prevent hot fluid from flowing through the body of the mixter from the hot water inlet connection 18 to the cold water inlet connection 19 and likewise do not prevent cold fluid from flowing from the cold water inlet connection 19 to the hot water inlet connection 18.
Proposals have indeed already been made to associate thermostatic mixer devices with non-return valves in order to limit the above drawback.
However, present attempts at adding non-return valves to mixer devices have not given full satisfaction. Proposals have thus been made to place a non-return valve in each of the hot and cold water inlet ducts, upstream from the connections provided on the mixer body. However, this solution is expensive and unsightly. Further, it considerably complicates the operations of installation and maintenance.
Proposals have also been made to place non-return valves level with the hot and cold water inlet connections at the ends of connection tubes connected to the body of the mixer device. However, in this case the connections are not always accessible and maintenance becomes impossible.
Finally, proposals have also been made to place non-return valves in the body of the mixer device level with the hot and cold water inlet connections. They are then readily accessible and maintenance operations are easy. However, this construction gives rise to bulky apparatuses which are unsightly and expensive.
The present invention now seeks to provide a new mixer device including a thermostatic element and suitable for preventing any hot or cold water from reaching the cold or hot water inlet connections, respectively, while still being simple, reliable, and cheap to implement.